In the following sentence, four words or phrases have been printed in bold. One bold part in the sentence is not acceptable in Standard English. Pick up that part and mark its number. If there are no errors in the bold parts, mark (5) i.e. No error as the answer.

Progress in Covid vaccination is a tribute(A) to the success of science, in India and the world, in producing effective(B) vaccines in record time and to the unpresedented(C) mobilisation of resources to undertake(D) the largest ever mass vaccination of adults.